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Speaker tilt - distance, height and angle

13-03-2017, 05:05 PM

Hello to all,

I would like to improve the performance of my P3ESR and wonder if I should adjust the speaker "tilt". My listening distance is about 2.7m, head height about 65cm and speaker tweeter height about 95cm.
- Will the height difference creates a sound quality issue at this distance.
- How many degrees of "forward tilt" do I need to get the tweeter pointing toward my ears?
- can the speakers fall of the stand (currently using some blue tack between the stand and the speakers) with the tilt adjustment?
- are they any stand that incorporate an adjustable speaker plate?

Based on your listening distance figure, head height and speaker tweeter height, your P3ESRs will need to be tilted forward by about 6.34 degrees to put your ears directly on axis with the tweeter. The tilt angle theta can be estimated from the following trigonometric equation:

theta = atand((95-65)/270) = 6.34 degrees

Now, as the depth of the P3ESR cabinet (excluding speaker binding posts) is 180 mm, this means that, in order to get a 6.34 degree forward tilt, it is necessary to raise the rear edge of the cabinet bottom by 180*sin(6.34) = 19.9 mm.

As to whether the present height difference creates a sound quality issue at this listening distance, that will of course depend on a number of factors. Listening at 6.34 degrees below the axis of the tweeter will likely change the frequency response as heard at the listening location. In many speaker designs, a small dip could be present through the crossover region as a result of listening off-axis. This depends on the crossover topology and the order of the slopes of the filtered tweeter and woofer acoustic response functions.

Then there is the interaction of the P3ESR loudspeaker with the room. Changing the orientation of the P3ESR will likely change the nature of the sound reflections in the room, unless of course you happen to be listening in an anechoic chamber! :-)

So, considering what's going on, by tilting the P3ESR you are getting its designed on-axis sound quality more accurately sent to the listening position (which is a positive outcome), and you are changing the nature of the interaction of the P3ESR with the room environment. It would not be unreasonable to expect that there will be a difference in perceived sound quality between the un-tilted and the tilted configurations. Not knowing anything else about your room, I might anticipate that the sound quality will be improved to some degree. Whether or not you like what you hear, well, that's an assessment that you will be able to make when you listen.

I do not know how much difference you are likely to hear but you can try tilting the speaker a bit. Even though you now know the angle of tilt required it may be difficult for you to measure 6.4 degrees. I would try placing a thin book or pamphlet under the rear of the speaker. Be aware that a tilted arrangement is not as stable as when the speaker is perpendicular to the stand.

Also be aware that blu-tac is not kind to the veneer of the bottom of the speaker.

Comment

Thanks for looking into this. I've just added some foam bars (which are probably less than 10mm tick) at the back of the stands and the impact is already very impressive. I don't believe I can add more than that to get to 20mm without taking the risk of having the speakers fall over. I've ordered a digital level to properly measure the speaker angle. It would be nice to find some device that allow to hold the speaker and tilt/rotate securely, almost like a tripod camera ball head!

Comment

Unless I'm missing something here, I have to agree with Willem (post 4) that surely the answer (and safest way) is to just to buy a pair of speaker stands at the correct height.

If your ear height is 30cm lower than the tweeter then, if I were in your situation, I would just get some stands that were 30cm shorter to bring the tweeter to ear height. As you are based in the UK, there are at least two manufacturers of speaker stands (Hi Fi Racks & Something Solid) who will make them to order at whatever height you wish.

Best regards, Mike

Comment

In many speaker designs, a small dip could be present through the crossover region as a result of listening off-axis. This depends on the crossover topology and the order of the slopes of the filtered tweeter and woofer acoustic response functions.

Hello,

I'd be very interested if you have more information on this please? I noticed these dips on 2 different speakers while measuring them with Dirac. I thought this was because I measured the speakers at different mic heights at different positions, and off-axis, for averaging frequency response and trying to catch up room modes. Now, I wonder If it should be corrected, because it's more an arterfact of the measurements.

Thank you

Comment

thanks for for the suggestion of shorter stands. Unfortunately it's not going to work as I listen in different positions, so if I was getting some 30 cm stands I would need to make them titlt backward when I listen in a higher position. So in an ideal world, I'd need some 50cm stands with about 4 degree of tilt adjustment at the front and the back and the ability to secure the P3 to the stand plate.

Comment

I'd be very interested if you have more information on this please? I noticed these dips on 2 different speakers while measuring them with Dirac. I thought this was because I measured the speakers at different mic heights at different positions, and off-axis, for averaging frequency response and trying to catch up room modes. Now, I wonder If it should be corrected, because it's more an arterfact of the measurements.

Hello Sébastian,

There is a 1976 AES journal paper by Linkwitz, titled Active Crossover Networks for Noncoincident Drivers, which describes how a loudspeaker system's off-axis response can be affected by the use of noncoincident drivers. A PDF copy of this paper can be found here.

Comment

Here are some simulations of the on and off-axis frequency response functions for a theoretical two-way loudspeaker system.

Approximately like the P3ESR, the vertical separation between woofer and tweeter on the baffle is 125 mm. The tweeter is assumed to be connected with negative polarity relative to the woofer. The listening axis is assumed to be aligned with the tweeter's main axis. Five listening points have been defined, two being above the axis of the tweeter, one on the same axis, and two below the axis of the tweeter. The angles are positive for listening positions above the tweeter axis, and negative when below the tweeter axis. In the plot below, Point #0 = 0°, Point #1 = -12°, Point #2 = -6°, Point #3 = +6°, and Point #4 = +12°.

The woofer and tweeter response functions are modelled as 3rd-order acoustic low-pass and high-pass Butterworth frequency functions. It is seen that for listening locations below the tweeter axis, the response peaks in the crossover interaction region. For listening locations above the tweeter axis, the a dip in the summed response is quite apparent. When listening at 12° above the tweeter axis, there is also an almost perfect null in the response.

On the listening axis of the tweeter, we get a perfectly flat summed response. Note that this has been achieved by removing the time delay between the woofer and the tweeter for the on-axis case. This was accomplished by moving the woofer forward a few millimetres.

From the plotted response functions, it is quite evident that the 3rd-order acoustic Butterworth crossover produces very different results above and below the tweeter axis.

Comment

It's not practicable to measure using a microphone the (tiny) sonic contribution that a speaker stand could (theoretically) make to the overall sound that you hear in the listening room because of the difficulty of isolating the actual and dominant contribution of the speaker from the (theoretical) contribution from the stand.

A workaround is to attach an accelerometer to the speaker stand so that we can observe and measure the movement in the physical structure of the stand, and logically, if there is no physical movement in the stand it cannot generate sound, since sound is the consequence of physical movement. No movement, no sound.

I have begun to make some measurements of the movement of the legs of various stands using precision B&K accelerometers and charge amplifiers when the speaker/stand is driven from a test signal. This makes comparison easy.

My initial impression is that there is, obviously, some (tiny) movement of the stand's legs but that this movement, relative to that of the sound generated by the speaker, is of a very low level indeed. What does seem to be an early result is that the interface between the bottom of the speaker cabinet and the top plate of the stand seems to have a measurable difference on the energy transmitted to the stand. How that could, theoretically, translate into a difference in sonic contribution from the stand remains to be seen.

I suspect, but of course objective measurements may prove otherwise, that the contribution of the 'sound' of the stand relative to the sound of the speaker itself, may be one percent or less, which I'd say for all practical purposes means that the nature and design of the stand makes an imperceptible sonic contribution to the overall experience. However, as you can see from the picture below, the difference in height alone could and will have a dramatic influence on perceived sound, even for stands of identical construction but differing height.

This may be the first time that speaker stands have been objectively compared. We really owe it to ourselves to put the subject on a serious footing. It's not good that this hasn't been done before, to the best of my knowledge.

Comment

I would not want to tilt my speakers because they could easier fall from the stands. Here is a diy project with height adjustable stand with a provision for tilt. I would only build something likes this for adjusting the height without tilt.

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Comment

If you want tiltable speaker stands you should probably have a look at pro audio stands. I would expect there to be some that allow you to do just this. Alternatively there may be stands with adjustable height just like camera tripods.

Comment

There is a 1976 AES journal paper by Linkwitz, titled Active Crossover Networks for Noncoincident Drivers, which describes how a loudspeaker system's off-axis response can be affected by the use of noncoincident drivers. A PDF copy of this paper can be found here.

Comment

My initial impression is that there is, obviously, some (tiny) movement of the stand's legs but that this movement, relative to that of the sound generated by the speaker, is of a very low level indeed. What does seem to be an early result is that the interface between the bottom of the speaker cabinet and the top plate of the stand seems to have a measurable difference on the energy transmitted to the stand. How that could, theoretically, translate into a difference in sonic contribution from the stand remains to be seen.

I suspect, but of course objective measurements may prove otherwise, that the contribution of the 'sound' of the stand relative to the sound of the speaker itself, may be one percent or less, which I'd say for all practical purposes means that the nature and design of the stand makes an imperceptible sonic contribution to the overall experience. However, as you can see from the picture below, the difference in height alone could and will have a dramatic influence on perceived sound, even for stands of identical construction but differing height.

This may be the first time that speaker stands have been objectively compared. We really owe it to ourselves to put the subject on a serious footing. It's not good that this hasn't been done before, to the best of my knowledge.

I might be wrong but I was always under the impression that the thing is not whether or how much the stands actually move, excited by the speaker's cabinet vibration, thus generating their own sound, but whether the stand (or the type of isolation between the stand and the speaker) can in fact influence the behavior of the speaker cabinet itself, specifically the way it moves, thus changing the sound of the speaker. Possible way to measure if that phenomenon could occur in real life is putting the accelerometer on the speaker cabinet and see if its movements change depending on the speaker stand and/or isolation.